Use of the "is" statement

[Delaney, Timothy (Tim)]

Maric Michaud wrote:

> Le Friday 27 June 2008 18:26:45 Christian Heimes, vous avez écrit :
>> Ask yourself if you are interested if f.tell() returns exactly the
>> same 0 object ("is") or a number that is equal to 0 ("==").
> 
> That said, "f.tell() == 0" and "f.tell() != 0" should be written
> "f.tell()" and "not f.tell()" in python.
> 
> if not f.tell() :
>     print 'at the beginning of the file"

No, because semantically you're not using the result of f.tell() as a boolean value. tell() returns a *position*, and he is checking for a particular position.

If he'd instead been testing for f.tell() == 2, would you have advisd that he use "if f.tell()"?

Ignoring the triviality of the below code, would you suggest refactoring:

for i, v in enumerate(iterable):
    if i == 0:
        doSomethingSpecial()
    else:
        print i

as:

for i, v in enumerate(iterable):
    if not i:
        doSomethingSpecial()
    else:
        print -i

?

Tim Delaney